Binary String Functions and Operators
String Operators
SQL defines some string functions that use keywords, rather than commas, to separate arguments.
- octet_length(string)
Description: Specifies the number of bytes in a binary string.
Return type: int
Example:
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gaussdb=# SELECT octet_length(E'jo\\000se'::bytea) AS RESULT; result -------- 5 (1 row)
- overlay(string placing string from int [for int])
Description: Replaces substrings.
Return type: bytea
Example:
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gaussdb=# SELECT overlay(E'Th\\000omas'::bytea placing E'\\002\\003'::bytea from 2 for 3) AS RESULT; result ---------------- \x5402036d6173 (1 row)
- position(substring in string)
Description: Specifies the position of a specified substring.
Return type: int
Example:
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gaussdb=# SELECT position(E'\\000om'::bytea in E'Th\\000omas'::bytea) AS RESULT; result -------- 3 (1 row)
- substring(string [from int] [for int])
Description: Truncates a substring.
Return type: bytea
Example:
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gaussdb=# SELECT substring(E'Th\\000omas'::bytea from 2 for 3) AS RESULT; result ---------- \x68006f (1 row)
- substr(string, from int [, for int])
Description: Truncates a substring.
Return type: bytea
Example:
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gaussdb=# select substr(E'Th\\000omas'::bytea,2, 3) as result; result ---------- \x68006f (1 row)
- trim([both] bytes from string)
Description: Removes the longest string containing only bytes from the start and end of string.
Return type: bytea
Example:
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gaussdb=# SELECT trim(E'\\000'::bytea from E'\\000Tom\\000'::bytea) AS RESULT; result ---------- \x546f6d (1 row)
Other Binary String Functions
GaussDB provides common syntax used for calling functions.
- btrim(string bytea,bytes bytea)
Description: Removes the longest string containing only bytes from the start and end of string.
Return type: bytea
Example:
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gaussdb=# SELECT btrim(E'\\000trim\\000'::bytea, E'\\000'::bytea) AS RESULT; result ------------ \x7472696d (1 row)
- get_bit(string, offset)
Description: Extracts bits from a string.
Return type: int
Example:
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gaussdb=# SELECT get_bit(E'Th\\000omas'::bytea, 45) AS RESULT; result -------- 1 (1 row)
- get_byte(string, offset)
Description: Extracts bytes from a string.
Return type: int
Example:
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gaussdb=# SELECT get_byte(E'Th\\000omas'::bytea, 4) AS RESULT; result -------- 109 (1 row)
- set_bit(string,offset, newvalue)
Description: Sets bits in a string.
Return type: bytea
Example:
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gaussdb=# SELECT set_bit(E'Th\\000omas'::bytea, 45, 0) AS RESULT; result ------------------ \x5468006f6d4173 (1 row)
- set_byte(string,offset, newvalue)
Description: Sets bytes in a string.
Return type: bytea
Example:
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gaussdb=# SELECT set_byte(E'Th\\000omas'::bytea, 4, 64) AS RESULT; result ------------------ \x5468006f406173 (1 row)
- rawcmp(raw, raw)
Description: Specifies the raw data type comparison function.
Parameters: raw, raw.
Return type: integer
- raweq(raw, raw)
Description: Specifies the raw data type comparison function.
Parameters: raw, raw.
Return type: Boolean
- rawge(raw, raw)
Description: Specifies the raw data type comparison function.
Parameters: raw, raw.
Return type: Boolean
- rawgt(raw, raw)
Description: Specifies the raw data type comparison function.
Parameters: raw, raw.
Return type: Boolean
- rawin(cstring)
Description: Specifies the raw data type parsing function.
Parameter: cstring.
Return type: bytea
- rawle(raw, raw)
Description: Specifies the raw data type parsing function.
Parameters: raw, raw.
Return type: Boolean
- rawlike(raw, raw)
Description: Specifies the raw data type parsing function.
Parameters: raw, raw.
Return type: Boolean
- rawlt(raw, raw)
Description: Specifies the raw data type parsing function.
Parameters: raw, raw.
Return type: Boolean
- rawne(raw, raw)
Description: Compares whether the raw types are the same.
Parameters: raw, raw.
Return type: Boolean
- rawnlike(raw, raw)
Description: Checks whether the raw type matches the pattern.
Parameters: raw, raw.
Return type: Boolean
- rawout(bytea)
Description: Specifies the RAW output API.
Parameter: bytea
Return type: cstring
- rawsend(raw)
Description: Converts the bytea type to the binary type.
Parameter: raw
Return type: bytea
- rawtohex(text)
Description: Converts the raw format to the hexadecimal format.
Parameter: text
Return type: text
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